In the movie The Concussion, American football is a very popular sport in the United States and also very dangerous. Unlike European football, American is a very contact sport, so players have brain injuries.
That is discovered thanks to a doctor, Bennet Omalu, who begins to investigate when a very famous player dies young. He studies his brain and discovers why he has died and many players commit suicide.
Discover that the players have a disease that comes from the blows and that causes them many problems. That is why, he begins to fight for the disease to be known and for players to protect themselves.
Their fight is not going to be easy as there are many interests around American football and nobody wants to be publicized negatively of a sport that moves millions of dollars every year in the United States.